That is the later version of the AKG K240M's. I think they ended production of the K240Ms in the late 90s early early 2000s. [They started the K240Ms in the mid-80s if I'm not mistaken]. I've had both styles [not at the same time] and they sound the same to me. From what I've read there is no discernible sound difference between the two styles. Looking at the pictures my guess they are mid-90s. There are two main versions/styles that matter and the rest are just cosmetic changes. Both sound the same and it really doesn't matter what version they are long as they are in working order.

I plugged my K240M into my Heed CanAmp to listen to the radio. I noticed the K240M sounded very low on the 9'o clock position. I then turned the volume up the 12 o clock position, and got decent sound.

Next I plugged in my AKG K240 MKII (55ohm), the sound was more louder than the K240M at the 9'o clock position. And the K240 MKII will sound way too loud at the 12' o clock position.